1. Field of the Invention
The present invention relates generally to an integrated system for detecting and eliminating in realtime phase distortions in a wavefront, and more particularly pertains to a system of the aforementioned nature in which the components for detecting wavefront distortions and the components for correcting the detected wavefront distortions are integrated into one unit.
2. Discussion of the Prior Art
The resolution of ground based optical imaging systems is severely limited by random wavefront tilts and phase changes produced by atmospheric turbulence. The resolution of such optical systems is usually limited to one or two arc seconds by the atmosphere and may be considerably improved if the atmospheric distortion can be measured and corrected in real-time prior to recording of the image on tape or film.
Present systems for real-time optical wavefront compensation employ discrete components to perform the wavefront sensing and wavefront compensation functions. A system this type is diclosed in Hardy U.S. Pat. No. 3,923,400 for REAL-TIME WAVEFRONT CORRECTION SYSTEM, which is expressly incorporated by reference herein. In the approach disclosed by this patent, a wavefront being imaged is directed onto an AC, lateral shearing interferometer which measures in real time the relative phase differences between different areas of the wavefront. The constructional details of a suitable lateral AC shearing interferometer are disclosed in Wyant U.S. Pat. No. 3,829,219 for SHEARING INTERFEROMETER. The measured phase differences in the form of electrical signals are then directed to a separate analog data processor circuit which generates a second set of electrical signals, the amplitudes of which are proportional to the required phase corrections at the different areas of the wavefront. The second set of signals is then directed to a separate phase corrector element upon which the wavefront is incident to eliminate the relative phase differences therein. One separate phase corrector element disclosed by this patent is a mirror having an array of piezoelectric elements incorporated therein which function to selectively deform the mirror surface to eliminate phase distortions in the wavefront. The constructional details of an active piezoelectric mirror of this nature are disclosed in U.S. Pat. No. 3,904,274 for MONOLITHIC PIEZOELECTRIC WAVEFRONT PHASE MODULATOR.
The approach pursued by the aforementioned prior art results in two severe restrictions on real-time wavefront compensation systems. First, the spatial resolution at which optical wavefronts can be measured and corrected is limited, and secondly the cost and complexity of the system become prohibitive when the number of discrete components exceeds a few hundred. For example, compensation of a four meter astronomical telescope for atmospheric turbulence utilizing the prior art approach would require upwards of one thousand independent actuator channels.